/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableMap.IteratorBasedImmutableMap;
import com.google.j2objc.annotations.WeakOuter;
import java.util.Map;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

/**
 * A {@code RegularImmutableTable} optimized for dense data.
 */
@GwtCompatible
@Immutable
final class DenseImmutableTable<R, C, V> extends RegularImmutableTable<R, C, V> {
    private final ImmutableMap<R, Integer> rowKeyToIndex;
    private final ImmutableMap<C, Integer> columnKeyToIndex;
    private final ImmutableMap<R, Map<C, V>> rowMap;
    private final ImmutableMap<C, Map<R, V>> columnMap;
    private final int[] rowCounts;
    private final int[] columnCounts;
    private final V[][] values;
    // For each cell in iteration order, the index of that cell's row key in the row key list.
    private final int[] cellRowIndices;
    // For each cell in iteration order, the index of that cell's column key in the column key list.
    private final int[] cellColumnIndices;

    DenseImmutableTable(ImmutableList<Cell<R, C, V>> cellList, ImmutableSet<R> rowSpace, ImmutableSet<C> columnSpace) {
        @SuppressWarnings("unchecked")
        V[][] array = (V[][]) new Object[rowSpace.size()][columnSpace.size()];
        this.values = array;
        this.rowKeyToIndex = Maps.indexMap(rowSpace);
        this.columnKeyToIndex = Maps.indexMap(columnSpace);
        rowCounts = new int[rowKeyToIndex.size()];
        columnCounts = new int[columnKeyToIndex.size()];
        int[] cellRowIndices = new int[cellList.size()];
        int[] cellColumnIndices = new int[cellList.size()];
        for (int i = 0; i < cellList.size(); i++) {
            Cell<R, C, V> cell = cellList.get(i);
            R rowKey = cell.getRowKey();
            C columnKey = cell.getColumnKey();
            int rowIndex = rowKeyToIndex.get(rowKey);
            int columnIndex = columnKeyToIndex.get(columnKey);
            V existingValue = values[rowIndex][columnIndex];
            checkArgument(existingValue == null, "duplicate key: (%s, %s)", rowKey, columnKey);
            values[rowIndex][columnIndex] = cell.getValue();
            rowCounts[rowIndex]++;
            columnCounts[columnIndex]++;
            cellRowIndices[i] = rowIndex;
            cellColumnIndices[i] = columnIndex;
        }
        this.cellRowIndices = cellRowIndices;
        this.cellColumnIndices = cellColumnIndices;
        this.rowMap = new RowMap();
        this.columnMap = new ColumnMap();
    }

    /**
     * An immutable map implementation backed by an indexed nullable array.
     */
    private abstract static class ImmutableArrayMap<K, V> extends IteratorBasedImmutableMap<K, V> {
        private final int size;

        ImmutableArrayMap(int size) {
            this.size = size;
        }

        abstract ImmutableMap<K, Integer> keyToIndex();

        // True if getValue never returns null.
        private boolean isFull() {
            return size == keyToIndex().size();
        }

        K getKey(int index) {
            return keyToIndex().keySet().asList().get(index);
        }

        @Nullable
        abstract V getValue(int keyIndex);

        @Override
        ImmutableSet<K> createKeySet() {
            return isFull() ? keyToIndex().keySet() : super.createKeySet();
        }

        @Override
        public int size() {
            return size;
        }

        @Override
        public V get(@Nullable Object key) {
            Integer keyIndex = keyToIndex().get(key);
            return (keyIndex == null) ? null : getValue(keyIndex);
        }

        @Override
        UnmodifiableIterator<Entry<K, V>> entryIterator() {
            return new AbstractIterator<Entry<K, V>>() {
                private int index = -1;
                private final int maxIndex = keyToIndex().size();

                @Override
                protected Entry<K, V> computeNext() {
                    for (index++; index < maxIndex; index++) {
                        V value = getValue(index);
                        if (value != null) {
                            return Maps.immutableEntry(getKey(index), value);
                        }
                    }
                    return endOfData();
                }
            };
        }
    }

    private final class Row extends ImmutableArrayMap<C, V> {
        private final int rowIndex;

        Row(int rowIndex) {
            super(rowCounts[rowIndex]);
            this.rowIndex = rowIndex;
        }

        @Override
        ImmutableMap<C, Integer> keyToIndex() {
            return columnKeyToIndex;
        }

        @Override
        V getValue(int keyIndex) {
            return values[rowIndex][keyIndex];
        }

        @Override
        boolean isPartialView() {
            return true;
        }
    }

    private final class Column extends ImmutableArrayMap<R, V> {
        private final int columnIndex;

        Column(int columnIndex) {
            super(columnCounts[columnIndex]);
            this.columnIndex = columnIndex;
        }

        @Override
        ImmutableMap<R, Integer> keyToIndex() {
            return rowKeyToIndex;
        }

        @Override
        V getValue(int keyIndex) {
            return values[keyIndex][columnIndex];
        }

        @Override
        boolean isPartialView() {
            return true;
        }
    }

    @WeakOuter
    private final class RowMap extends ImmutableArrayMap<R, Map<C, V>> {
        private RowMap() {
            super(rowCounts.length);
        }

        @Override
        ImmutableMap<R, Integer> keyToIndex() {
            return rowKeyToIndex;
        }

        @Override
        Map<C, V> getValue(int keyIndex) {
            return new Row(keyIndex);
        }

        @Override
        boolean isPartialView() {
            return false;
        }
    }

    @WeakOuter
    private final class ColumnMap extends ImmutableArrayMap<C, Map<R, V>> {
        private ColumnMap() {
            super(columnCounts.length);
        }

        @Override
        ImmutableMap<C, Integer> keyToIndex() {
            return columnKeyToIndex;
        }

        @Override
        Map<R, V> getValue(int keyIndex) {
            return new Column(keyIndex);
        }

        @Override
        boolean isPartialView() {
            return false;
        }
    }

    @Override
    public ImmutableMap<C, Map<R, V>> columnMap() {
        return columnMap;
    }

    @Override
    public ImmutableMap<R, Map<C, V>> rowMap() {
        return rowMap;
    }

    @Override
    public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
        Integer rowIndex = rowKeyToIndex.get(rowKey);
        Integer columnIndex = columnKeyToIndex.get(columnKey);
        return ((rowIndex == null) || (columnIndex == null)) ? null : values[rowIndex][columnIndex];
    }

    @Override
    public int size() {
        return cellRowIndices.length;
    }

    @Override
    Cell<R, C, V> getCell(int index) {
        int rowIndex = cellRowIndices[index];
        int columnIndex = cellColumnIndices[index];
        R rowKey = rowKeySet().asList().get(rowIndex);
        C columnKey = columnKeySet().asList().get(columnIndex);
        V value = values[rowIndex][columnIndex];
        return cellOf(rowKey, columnKey, value);
    }

    @Override
    V getValue(int index) {
        return values[cellRowIndices[index]][cellColumnIndices[index]];
    }

    @Override
    SerializedForm createSerializedForm() {
        return SerializedForm.create(this, cellRowIndices, cellColumnIndices);
    }
}
